Researchers tracked nearly 3.7 million births over three decades in a Swedish study published in JAMA Pediatrics showing children born with rare congenital infections known as TORCH pathogens face an elevated risk of autism and intellectual disability.
Karolinska Institutet Registry Tracking Millions of Births
Researchers tracked health and education records for 3,666,002 individuals born in Sweden between 1987 and 2021. Among that population, 975 people were diagnosed with congenital infections. These pathogens belong to the clinical group designated as TORCH, which encompasses toxoplasmosis, syphilis, rubella, cytomegalovirus (CMV), and herpes simplex virus. Unlike common prenatal illnesses, these specific infectious agents can cross the placenta and directly reach a developing fetus.
Individuals with TORCH infections recorded 5.39 autism diagnoses per 1 000 person-years, whereas uninfected individuals had a rate of 1.71 per 1 000 person-years. The risk of developing an intellectual disability was even more pronounced, showing a rate more than seven times higher than that of the general population. Among those with TORCH infections, 54.6% were male, compared with 51.4% of those without infections.
For intellectual disability, the incidence reached 8.22 per 1 000 person-years among those with a TORCH infection, contrasting with 0.68 for those lacking the infection.
Intellectual Disability Severity Lowers Academic Performance
As the severity of intellectual disability increased, the associated hazard ratio climbed sharply. Autism diagnoses frequently co-occurred with intellectual disability among the affected cohort.
The developmental effects also registered in classroom performance. Even children who never received a formal diagnosis of autism or intellectual disability demonstrated lower academic performance, pointing to subtle cognitive differences across the affected group.
Sibling Comparisons Rule Out Shared Familial Confounding
To determine whether shared genetics or household environments might explain the results, researchers tested the data directly by comparing infected children with their own uninfected siblings. The elevated risk persisted across sibling models, indicating that shared familial traits alone did not drive the outcomes. Hazard ratios were similar or higher in the sibling comparisons, a pattern that argues against the association being explained by shared family confounding.
“In contrast to studies of common maternal infections, where associations with autism are largely explained by familial confounding, our findings persisted after sibling adjustment.”
Study authors, via CIDRAP
Despite the strong relative risks within the exposed group, researchers emphasized that TORCH infections remain rare at the population level.
Experts Urge Vaccines to Prevent Cytomegalovirus
Cytomegalovirus accounted for approximately half of all observed TORCH cases in the Swedish cohort. Experts writing outside the study highlighted the preventative potential of immunization programs. Mark Schleiss, a pediatric infectious disease physician at the University of Minnesota School of Medicine, argued that public health systems should focus more heavily on cytomegalovirus prevention.
“We need to acknowledge that one solution (for at least a subset of autism spectrum disorders) is to administer more vaccines.”
Mark Schleiss, MD, University of Minnesota School of Medicine
Schleiss pointed out that public awareness of cytomegalovirus remains disturbingly low, adding support for legislative efforts such as the Stop CMV Act of 2025 in the United States. Only two states, Minnesota and Connecticut, currently screen for congenital cytomegalovirus in all newborns.